More than a fifth (22 per cent) had been turning to alcohol more often, and the same percentage (22 per cent) said they had increased their caffeine intake.

Just under a fifth (19%) said they had lost their appetite and over one in 10 (11 per cent) said they had started to use, or increased their use, of anti-depressants.

Around nine per cent had had a relationship break down, while around seven per cent had started to take, or were taking more, prescription drugs.

One NASUWT member told the union: "My husband has left me because I'm always working", and another said that their teaching job had led to the breakdown of a 16-year marriage.

A third said: "I lose sleep worrying. I feel guilty if I am off sick or not working evenings and weekends."

More than half of those polled (56 per cent) by the NASUWT, which is meeting for its annual conference in Manchester, said that their job satisfaction has declined in the last 12 months, 37 per cent said it had stayed the same and the rest said it had improved.

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More than four-fifths of school staff (83 per cent) think that their job has had a negative impact on their health and wellbeing in the last 12 months, the survey also foundCredit: Fredrick Kippe / Alamy Stock Photo

A Department for Education spokesman said: "Teaching remains an attractive profession with more people joining the profession than leaving or retiring.

"Nevertheless we want teachers to have the freedom to do what they do best, inspire children to learn. We continue to work with teachers, unions and Ofsted to tackle unnecessary workload and challenge unhelpful practices that create extra work, including through an offer of targeted support to schools.

"Alongside this we are exploring ways to improve career progression for teachers to encourage them to stay in the profession.

"Where staff are struggling, we trust headteachers to take action to tackle the causes of stress and ensure they have the support they need."

NASUWT general secretary Chris Keates said: "It is clear that for too many teachers the job is taking an unacceptable toll on their health and wellbeing and that this is affecting all aspects of their personal and professional lives.

It is clear that for too many teachers the job is taking an unacceptable toll on their health

NASUWT general secretary Chris Keates

"If the majority of teachers are unable to relax away from work and feel constantly worn down and worried about work issues, then their mental and physical health is inevitably going to suffer and they will not be able to give their best to the children they teach."

The findings come after the general secretary of the Association of Teachers and Lecturers suggested that teachers are taking a pay cut to work a four-day week, just to keep up with their workload.

Dr Mary Bousted said she was aware of increasing numbers of school staff who are choosing to officially work part-time in order to get their planning and marking done.

"They spend Friday doing all their work so they can have a free weekend," she said. "Lots of people told me about that and that's happening more and more."

A recent study concluded that teachers in England work some of the longest hours in the profession in the developed world.

Half of the country's full-time teachers work 40-58 hours a week and a fifth work at least 60 hours a week, according to an analysis by the Education Policy Institute published last autumn.

The NASUWT online poll questioned around 4,300 members in February and March.